Preheat oven to 325 F.
Line cupcake pan with liners.
In a large microwave-safe bowl, combine chocolate chips and butter. Microwave on high on 30 second intervals, stirring in between until completely melted and smooth.
In a separate bowl, whisk together eggs, sugar, and vanilla until well mixed.
Slowly add egg mix to the chocolate mix, whisking well.
Slowly add in flour and mix until smooth.
Add batter to cupcake liners, filling them about 2/3 full.
Bake for 15-20 minutes, until toothpick comes clean.
Let cool in pan for 10 minutes before transferring to a cooling rack.